The present invention relates to an image forming apparatus and, more particularly, to a finisher incorporated in a copier for finishing copy sheets driven out of the copier.
It is a common practice with a copier or similar image forming apparatus to discharge a paper sheet carrying a document image toward a copy tray after the document image has been fixed on the sheet. The copier is operable with a finisher including a sorter for sorting copy sheets sequentially driven out of the copier to a plurality of bins, and a stapler for stapling the stacks of paper sheets loaded on the bins one after another. The sorter has been proposed in various forms as disclosed in, for example, Japanese Patent Laid-Open Publication Nos. 34855/1989 and 34864/1989 and U.S. Pat. No. 3,833,911. In this kind of sorter, a plurality of bins constitute copy trays for accommodating copy sheets sequentially discharged from the copier, and each has pins at opposite ends thereof in the widthwise direction of paper sheets. The pins of each bin are received in the grooves of helical cams to be movable up and down. As the helical cams are rotated, a required number of bins are sequentially brought to a position at which copy sheets driven out of the copier arrive. To guarantee the space for introducing paper sheets, the helical cams have their lead changed in the axial direction such that part thereof having a greater lead, i.e., spacing nearby bins by a greater distance faces a paper introducing mechanism. On the other hand, a jogger extends throughout the bins for positioning paper sheets sequentially discharged onto the bins. A stack of paper sheets neatly positioned by the jogger is stapled at one end in the widthwise direction thereof by the stapler which is located at one end in the widthwise direction of the bin.
The problem with the conventional sorter described above is that it can staple a paper stack only at a single position adjacent to one end of the paper stack with respect to the widthwise direction. Specifically, when a stack of paper sheets having a relatively great width are stapled only at a single position thereof, the resulting stack is apt to become loose when read or otherwise handled afterwards.